Silazane-based polymers such as polysilazanes or poly-metallo-silazanes are specific polymers capable of being transformed into a ceramic material. When such polymers are transformed into a ceramic material, there can be obtained ceramic materials which are excellent in heat resistance, abrasion resistance, corrosion resistance or the like and composed substantially of SiO.sub.2.
As is known, the silazane-based polymers have been widely utilized as a film-forming component for coating materials (Japanese Patent Application Laid-open Nos. 99327/1987 and 203476). In order to form a ceramic film on a substrate using the coating material containing the silazane-based polymer, there has been adopted a method which comprises applying the coating material onto the substrate to form a polymer film thereon and thereafter transforming the polymer film into a ceramic material.
However, such a conventional method for the ceramic-transformation of the silazane-based polymers, the polymer has to be calcined at a high temperature on the order of 900.degree. C. For this reason, there has arose such a problem that the resultant ceramic film tends to suffer from deficiencies such as voids, pinholes, cracks or the like.
In addition, in order to carry out the ceramic-transformation of the polysilazane-based polymer at a reduced temperature, there have been proposed a method in which the polymer film is calcined in an oxidation atmosphere (WO93/02472), and a method in which a mixture of polysilazane and polysiloxane is used (Japanese Patent Application Laid-open No. 73340/1994).
In these conventional methods, it is possible to transform the silazane-based polymer into a ceramic material at a temperature as low as 450.degree. C. and therefore produce a ceramic film having a good denseness and an excellent resistance to cracking. However, the temperature used in these conventional methods is still too high so as not to be applied to ceramic forming techniques in the fields of electronic products such as semiconductor devices or liquid crystal devices, plastic products or the like. Accordingly, the conventional methods cannot be utilized as ceramic forming techniques in these fields.
Further, in the afore-mentioned conventional methods for transforming the silazane-based polymer into a ceramic material, low molecular weight polymers are scattered around due to a high temperature required to calcine the polymer, so that there arises inconveniences such as loss of the polymer, contamination of calcining apparatuses used, or the like.